, 1887-05-01
NEW AND OLD BRIDGES.
VARIOUS STRUCTURES ACROSS sIa
STREAMS OF WATER.

-
The Now Harlem Bridge and How They
are Building It-The New bridge Across
East RIyer-somo Famous Bridges, Az
cient and Modern.
New York city is likely to be eventually
tho most famous In the world on account of
its bridges The one building over the Hnr-
lem river at One Hundred and Eighty-first
street will add to its Importance as n city OF
bridges, and another is contemplated across
East river above the Brooklyn bridge.
The foundntion for the center pier of the
bridge over the Harlem is approaching COM
pletion- When finished the bridge will be an
achievement worthy of the genius and time
expended upon 1t. 1t will consist of two
metallic arches, each $40 feet clear, one
OF which spans the entire width of the river
and the other the whole distance from ths
easterly bank Of the river to Sedgwick ave-
nue.. Each span consists of six separate steel
plate arches, spaced IA feet between center
md connected by brncing. The floor sys-
tenn is carried on vertical columns supported
by tho arches. The floor Is 80 feet wide,
and consists Of a roadway OF 50 feet and
two footwalks of 10 feet each. The grade Of
the roadway Is LEO feet above mean high tide.
The arched masonry approaches are as nearly
symmetrical at both ends as practicable.
In sinking the Foundation for the center
pier it was discovered that fifteen feet from
the surface of the water rock sloping down
ward at a sharp angle toward the center Of
the river would DO encountered. and on this
rock rest the soft mud and sand Of the river
bed. This necessitated the extensive uso of ex-
plOsives- Indeed, it is believed That In this
instance more rock was removed By blasting
than In any other similar worir(eyer under
taken. AT first they used dyfsInite exclu-
siyely; but the gases it generated caused the
men to complain OF severe headaches after
each firing. That and the peril of handling
IL were against it. Rackarock was then tried
with pleasanter results, Rackarock consists
OF two ingredients, a tiuid aud Il solid, shipped
in separate packages, each of which is abso-
lutely non explosive. When needed, the two
ingredients are combined by pouring q Ger.
tain proportion OF the fluid over the solid,
which Is contained in q bag of the usual
cartridge form 1t takes but a few seconds
for the oil to thoroughly saturate the cart
ridge. ono of the tied ends of which Is then
cut, the cloth case opened and tho fuse in
serted. Tho end is then retied, and the cart
ridge is ready for use in the ordinary way.
Tho bill authorizing the construction of the
new East river bridge passed congress in
March The structure will go from New
York city to Long Island by way of Black
WELLS Island. 1t is to be $50 feet high, span
ming either channel, will accommodate pas
senger and freight cars, and win also have a
footway. Sufficient capital is promised in
Europe to build il from the foundations Of
the piers to the last coating of paint. Its
starting place in New York is near the Grand
Central depot; it win DO ca~ntilever, like that
at Niagara, and win DO three and a half
miles long.
Il is designed Tor rapid transit in the true
sen9e OF the term. Trains will be run at
thirty miles an hour. AL vehicles will be
run over on platform cars designed for this
purpose. That it will develop and populate
Queens county and hong Island generally is
a certainty. Cantilever means a lever or sup
port for something at q cant or angle from a
wall beyond which 1t projects. In plain
words, IL Is like a bracket secured to the wall
from which 1t runs out for the purpose of
bearing up a cornicc or other material.
Niagara had the first notable cantilever
bridge. 1t has been complete and carrying
trains at speed for over two years. The road
way OF this bridge runs over the tops of the
towers. Since 1t has been completed another
similar to it has been built over the river at
st. John, n. d.
The greatest cantiiever bridge, however, is
the one now building over the Firth OF Forth,
Scotland. The Firth Ia an arm of the sea
frequented by Great Britain's largest iron
clads, and requires a bridge considerably